Benefit Plans (Components of net periodic cost (benefit)) (Details) - Pension Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 20	$ 25
Expected return on plan assets	(39)	(36)
Amortization of net actuarial (gain) loss	11	10
Settlement loss	1	0
Total net periodic pension cost (benefit)	$ (7)	$ (1)